A) Field of the Invention
The present invention relates to a probe unit and a manufacturing method thereof.
B) Description of the Related Art
Conventionally a probe unit having a plurality of leads projecting from a substrate and contacting with electrodes of a sample is known. In a probe unit disclosed in Japanese Laid-open Patent No. 2002-286755 (hereinafter called the Patent Document 1), tips of leads and their peripheral areas are bent by overdrive because the leads are projecting from a substrate. Therefore, the tips of the leads and the electrodes of the sample can be conducted firmly with a proper contacting pressure.
In the conventional probe unit as disclosed in the Patent Document 1, thicknesses of the leads are uniformed. Moreover, material for the leads and the thicknesses of the leads are designed in accordance with durability of the projection parts of the leads from the substrate and the above-described contacting pressure. Therefore, it is not easy for the probe unit according to the Patent Document 1 to be designed to have low electric resistance by forming the leads with material having low electric resistance and by making the thicknesses thick. In addition to that, widths of the leads are designed in accordance with a pitch of the electrodes of the sample. Therefore, narrowing the widths of the leads cannot lower the electric resistance of the leads. In this type of the probe unit, a frequency range that can be used in a continuity test will be narrow because of a high conductor loss.
On the other hand, Japanese Laid-open Patent No. 2003-57266 discloses a probe unit wherein leads are formed on a film, tips of the leads are projecting from the film, and the tips and the middle parts of the leads are made of different materials. In the probe unit according to the Patent Document 2, middle parts of the leads can be made of material having lower electrical resistance than their tips. That is, the frequency range of a signal that can be used in a continuity test can be widened by lowering conductor losses because the electrical resistance of the leads can be lowered.
However, the probe unit according to the Patent Document 2 is manufactured by forming leads on a supporting metal plate, contacting parts of the leads that are not projecting from a film with the film by adhesive, and separating the supporting metal plate. The leads on the supporting metal plate side will be plane because they are formed on the supporting metal plate. Moreover, the adhesive contacts the leads and the film; therefore, large steps cannot be formed on the film side of the leads. That is, widths of the leads in the probe unit according to the Patent Document 2 cannot be designed freely to lower the electrical resistance of the leads.